ABSTRACT Despite substantial evidence of adverse health effects resulting from exposure to welding fume, shipyard welders continue to have very high exposure levels. Dilution and local exhaust ventilation strategies designed to reduce exposure levels are available but not often used in shipyard environments, and welders' use of respiratory protection varies widely. This study is designed to develop and assess the effectiveness of a training intervention designed to increase shipyard workers' use of simple dilution ventilation strategies - and thereby reduce welding fume exposure -in confined and enclosed spaces. We will develop specific ventilation strategies using published best practice guidelines as well as through simple modeling of expected contaminant dispersion using a basic box model. Once these simple guidelines are developed, we will evaluate their effectiveness under real-world shipyard conditions, revise the guidelines as necessary to achieve expected performance, and then incorporate these guidelines into a training intervention based on the well-established Health Promotion Model. The intervention will emphasize overcoming potential barriers to ventilation use and address issues related to organizational support for ventilation and overall worksite safety climate. The onsite training intervention will include both classroom learning and hands-on application and evaluation of ventilation strategies. Three shipyards will be identified for intervention, with a target of 30 welders per shipyard. Each shipyard will undergo a six-month baseline assessment, during which subjects' exposures and use of ventilation will be assessed multiple times using three different techniques: observed work practices, air contaminant concentrations and self-reported ventilation use. The primary assessment measure will be monthly researcher observations of each subject's work activities and conditions and use of ventilation during the baseline period. Quantitative air samples and surveys of ventilation use, perceptions and knowledge will also be collected on each subject during the baseline period. After delivery of the training intervention, subjects' welding exposures will again be assessed for a period of six months via monthly researcher observations, quantitative air samples, and interview survey. We will analyze post-intervention changes in welding exposures using the three assessment measures to determine the effectiveness of workers' implementation of the strategies in the training intervention. The results will inform decisions regarding the utility of a worker-oriented training intervention designed to reduce occupational exposures through use of ventilation controls. The results will be prepared in a form that can be disseminated as practical ventilation and training guidelines for the shipyard industry, as well as presented for scientific publication.